A comparison of the amount and distribution of coronary arterial narrowing by atherosclerotic plaque at necropsy is described in each of 4 decades (31-70 years) of 60 male victims of sudden coronary death (SCD). Of 2,995 five-mm segments examined (mean 50 per patient) of the 4 major (left main [LM], left anterior descending [LAD], left circumflex [LC] and right) coronary arteries, no significant differences were observed in the mean percent of 5-mm long segments narrowed severely (76-100% in cross-sectional area [XSA]) in each decade: 33% in the 5 patients aged 31-40 years; 29% in the 27 patients aged 41-50 years; 26% in the 18 patients aged 51-60 years, and 30% in the 10 patients aged 61-70 years. The mean percent of 5-mm segments severely narrowed was significantly (p Less than .05) greater in the proximal halves than in the distal halves of the LAD, LC and right coronary arteries in only the 2 older decades. The mean percent of 5-mm segments minimally (0-25%) narrowed, however, was significantly higher in the younger than in the older decades. Thus, as groups, both young and old victims of SCD have similar amounts of severe coronary narrowing, but the younger victims have a greater proportion of their major coronary arteries minimally narrowed.